Cathode For Sodium-ion Batteries Research Articles

High-loading NaCrO2 @C nanofibers as binder-free cathode for high-stable sodium-ion batteries

A NaCrO2 @C flexible free-standing cathode is designed and fabricated via a facile electrospinning strategy, in which electrochemically active NaCrO2 nanoparticles homogeneously dispersed in the flexible carbon nanofibers. Serving as the binder-free cathode for sodium-ion batteries, the as-constructed NaCrO2@C flexible free-standing cathode delivers a long cycling life (81 % capacity retention after 1000 cycles) with a high loading (7.6 mg cm−2). The enhancements for sodium-ion insertion/desertion is assigned to the dramatically decrease the polarization between electrodes and avoid the volume expansion during high-rate cycling. The NaCrO2@C flexible free-standing cathode opens up exciting possibilities for the development of advanced flexible sodium-ion batteries with both excellent mechanical flexibility and electrochemical properties.

P/n-Type Polyimide Covalent Organic Frameworks for High-Performance Cathodes in Sodium-Ion Batteries.

Covalent organic frameworks (COFs) are viewed as promising organic electrode materials for metal-ion batteries due to their structural diversity and tailoring capabilities. In this work, firstly using the monomers N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine (TPDA) and terephthaldehyde (TA), p-type phenylenediamine-based imine-linked TPDA-TA-COF is synthesized. To construct a bipolar redox-active, porous and highly crystalline polyimide-linked COF, i.e., TPDA-NDI-COF, n-type 1,4,5,8-naphthalene tetracarboxylic dianhydride (NDA) molecules are incorporated into p-type TPDA-TA-COF structure via postsynthetic linker exchange method. This tailored COF demonstrated a wide potential window (1.03.6 V vs Na+/Na) with dual redox-active centers, positioning it as a favorable cathode material for sodium-ion batteries (SIBs). Owing to the inheritance of multiple redox functionalities, TPDA-NDI-COF can deliver a specific capacity of 67 mAh g-1 at 0.05 A g-1, which is double the capacity of TPDA-TA-COF (28 mAh g-1). The incorporation of carbon nanotube (CNT) into the TPDA-NDI-COF matrix resulted in an enhancement of specific capacity to 120 mAh g-1 at 0.02 A g-1. TPDA-NDI-50%CNT demonstrated robust cyclic stability and retained a capacity of 92 mAh g-1 even after 10 000 cycles at 1.0 A g-1. Furthermore, the COF cathode exhibited an average discharge voltage of 2.1 V, surpassing the performance of most reported COF as a host material.

Air-stable manganese-based layered oxide cathode enabled by surface modification and doping strategy for advanced sodium-ion batteries

P2-type layered oxide materials have attracted widespread attention as advanced cathodes for sodium-ion batteries due to their excellent rate potential and attractive cost-effectiveness. However, the unexpected dissolution of transition metal (TM) ions and the annoying Jahn-Teller effect leading to rapid capacity fading and low capacity remain obstacles to their commercial applications. To tackle these handicaps, we introduced a synergistic effect based on surface modification and doping strategies to obtain air-stable sodium carbonate (Na2CO3) protective aluminum (Al)-doped manganese-based layered oxide cathode. The surface Na2CO3 nanolayer is created by converting residual alkali ions, which enhances the air stability of the cathode and scavenges hydrofluoric acid into the fluoride-rich cathode electrolyte interphase layer during cycling, resulting in a steady interfacial interaction. In addition, Al doping causes TMO6-octahedral shrinkage and inhibits structural distortion, thereby affecting structural evolution and phase transition. These findings provide valuable insights into improving the performance of layer oxide cathodes for next-generation low-cost batteries.

Topography control and component design strategies to enhance electrochemical performance of O3-Type cathode materials for Sodium-ion batteries

Layered transition metal oxides (NaxTMO2, 0 < x ≤ 1) are considered one of the most promising cathodes for Sodium-ion batteries (SIBs) due to their high theoretical capacity and operability. However, NaxTMO2 still faces significant challenges, including poor kinetic performance and low energy efficiency. Herein, in order to enhance the kinetics of NaNi1/3Fe1/3Mn1/3O2 (NaNFMO), topography control and component design were proposed: First, Cu doping (Cu-NaNFMO) was used to expand lattice channels and improve “flat sheet” of layered oxide, which synergistically enhanced transport kinetics of Na+. Second, Co coating (NaNFMO@Co) reacted with surface residue to form a fast-ionic conductor NaxCoO2 (0 < x ≤ 1), which inhibited interfacial side reactions and enhanced transport kinetics of Na+. Furthermore, the presence of strong Cu-O bonds in Cu-NaNFMO and fast-ionic conductor NaxCoO2 in NaNFMO@Co led to better electrochemical redox performance, the initial charge specific capacity of NaNFMO was increased from 141.5 mAh g⁻1 to 145.8 mAh g⁻1 and 144 mAh g⁻1, with capacity retention improving by nearly 10 % after 100 cycles. Furthermore, NaNFMO@Co improves ICE from 90.56 % to 93.57 %. With the improved kinetics, the DCR of pouch cells decreased, and the energy efficiency increased from 93.3 % to 94 % and 95.7 %.

Acid-assisted synthesis of core-shell Prussian blue cathode for sodium-ion batteries

In recent years, core–shell structured Prussian Blue Analogues (PBAs) have been considered as highly promising cathode materials for sodium-ion batteries. Reducing production costs and simplifying the preparation method for core–shell PBAs have also become crucial considerations. This paper presents a novel approach for the first time: by acid-treating the as-synthesized solution from a simple coprecipitation reaction, a high-crystallinity, sodium-rich Mn2+-doped iron hexacyanoferrate (Fe/MnHCF) shell material is self-grown on the surface of manganese hexacyanoferrate (MnHCF). This method significantly improves the electrochemical properties of the MnHCF material. The core–shell structured PBA exhibits excellent cycling performance (with a capacity retention of 95.5 % for 400 cycles at 1 A/g) and high rate performance (134.2mAh/g@10 mA/g, 95.2mAh/g@1 A/g). In this article, we explore the growth mechanism of the high-sodium content, high-crystallinity shell structure and introduce a green chelating agent that is better suited for the crystallization of Mn and Fe-type PBA systems. Our study demonstrates that Mn2+ doping enhances the conductivity of the shell material. Meanwhile, the heterojunction structure of MnHCF@Fe/MnHCF conducive to charge separation and migration. This straightforward synthesis strategy offers a novel approach for fabricating high-performance core–shell structured Prussian Blue Analogue materials.

Achieving Stable Cycling Performance in a P2-Type Layered Oxide Cathode through a Synergic Li/Zn Doping for Sodium-Ion Batteries.

It has been suggested that sodium layered transition metal oxides could potentially serve as excellent cathodes for sodium-ion batteries (SIBs) because of their appropriate operating potentials and high capacities. However, the growing reliance on energy requirements has necessitated a higher energy density of SIBs. It has been demonstrated that activating oxygen-related activities for SIBs is a viable method to improve energy density. Herein, we suggest applying the synergy of Li and Zn codoping to activate the anionic redox reactions (ARRs) and improve their reversibility in Na0.75Ni0.3Mn0.7O2. The dual ion doping alleviates the phase transition and inhibits the Na+/vacancy arrangements, consequently improving the rate capacity and cyclic stability. The Na0.75Li0.15Ni0.1Zn0.05Mn0.7O2 delivers a discharge capacity of 134 mA h g-1 and no significant capacity loss at 100 mA g-1 between 2 and 4.5 V after 200 cycles. More importantly, the density functional theory (DFT) calculation proves that the codoping strategy triggers more ARRs compared to single-element doping, thereby providing enhanced capacity. The codoping induced oxygen redox strategies will create a new path for rational design of cathodes to enhance the energy density for SIBs.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials

AbstractSodium‐ion batteries (SIBs) as a promising technology for large‐scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode‐electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra‐stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM‐CS‐GMg) cathode material in which a Mg‐free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg‐hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered‐to‐rock‐salt phase transition and the resultant microcracks. Besides, the less formation of high‐valence TM ions on the surface contributes to a stable cathode‐electrolyte interface. The as‐prepared NCM‐CS‐GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Surface Gradient Desodiation Chemistry in Layered Oxide Cathode Materials.

Sodium-ion batteries (SIBs) as a promising technology for large-scale energy storage have received unprecedented attention. However, the cathodes in SIBs generally suffer from detrimental cathode-electrolyte interfacial side reactions and structural degradation during cycling, which leads to severe capacity fade and voltage decay. Here, we have developed an ultra-stable Na0.72Ni0.20Co0.21Mn0.55Mg0.036O2 (NCM-CS-GMg) cathode material in which a Mg-free core is encapsulated by a shell with gradient distribution of Mg using coprecipitation method with Mg-hysteretic cascade feedstock followed by calcination. From the interior to outer surface of the shell, as the content of electrochemically inactive Mg gradually increases, the Na+ deintercalation amount gradually decreases after charged. Benefiting from this surface gradient desodiation, the surface transition metal (TM) ion migration from TM layers to Na layers is effectively inhibited, thus suppressing the layered-to-rock-salt phase transition and the resultant microcracks. Besides, the less formation of high-valence TM ions on the surface contributes to a stable cathode-electrolyte interface. The as-prepared NCM-CS-GMg exhibits remarkable cycling life over 3000 cycles with a negligible voltage drop (0.127 mV per cycle). Our findings highlight an effective way to developing sustainable cathode materials without compromising on the initial specific capacity for SIBs.

Layered Structure Modification of Sodium Vanadate through Ca/F Co‐Doping for Enhanced Energy Storage Performance

AbstractVanadate materials are promising for sodium‐ion batteries (SIBs) due to their low cost, high capacity, and high power characteristics enabled by vanadium's multiple oxidation states. However, their development is hindered by poor conductivity, suboptimal high‐rate performance, and limited cycle life. In this work, a layered structure modification strategy involving Ca/F co‐doping in sodium vanadate Na2CaV2O6F (CVF) is proposed to address these issues. Through a combination of experiments and density functional theory calculations, it is demonstrated that Ca/F synergies enhance the Na layer spacing in CVF, resulting in reduced crystal water content and volume shrinkage compared to Na2V2O6 (NVO). Additionally, Ca/F incorporation significantly mitigates the diffusion potential of Na+ within the material framework. The unmodified CVF sample exhibits a high reversible capacity of 220 mAh g−1 at 10 mA g−1 and an excellent rate capacity of 65.78 mAh g−1 at 400 mA g−1. Furthermore, the cathode material maintains a capacity of up to 138 mAh g−1 at 200 mA g−1 and retains 104.88 mAh g−1 after 100 cycles within the voltage range of 1.5−4.0 V. These findings enhance the understanding of the crystal structure of NVO cathode materials and pave the way for the rational design of high‐quality vanadate cathodes for SIBs.

Synthesis of a Sodium-Ion Cathode Material Na3Fe2(SO4)3F with the Help of Fluorine Element.

The development of cathode materials has always been one of the most crucial areas of research in the field of sodium-ion batteries. Sulfate-based polyanionic materials, known for their high working voltage characteristics, have received widespread attention. In this work, a fluoro-sulfate sodium-ion battery cathode material, Na3Fe2(SO4)3F modified with carbon nanotubes, was developed using a low-temperature solid-state annealing method. This Na3Fe2(SO4)3F cathode exhibits an exceptionally high voltage of 3.77 V, excellent discharge capacity (102 mAh/g at 0.1C), and good rate capability. This material broadens the research directions for cathode materials and holds promise as a foundation for the further development of high-performance sodium-ion batteries.

2D Covalent Organic Framework Covalently Anchored with Carbon Nanotube as High-Performance Cathodes for Lithium and Sodium-Ion Batteries.

Covalent organic frameworks (COFs), featuring structural diversity, permanent porosity, and functional versatility, have emerged as promising electrode materials for rechargeable batteries. To date, amorphous polymer, COF, or their composites are mostly explored in lithium-ion batteries (LIBs), while their research in other alkali metal ion batteries is still in infancy. This can be due to the challenges that arise from large volume changes, slow diffusion kinetics, and inefficient active site utilization by the large Na+ or K+ ion. Herein, microwave-assisted imide-based 2D COF, TAPB-NDA covalently connected with amine-functionalized carbon nanotubes (TAPB-NDA@CNT) targeting the application in both Li-/Na-ion batteries, is synthesized. As-synthesized, TAPB-NDA@CNT50 displays the good performance as LIB cathode with a specific capacity of ≈138mAhg-1 at 25mAg-1, long cycling stability (81.2% retention after 2000 cycles at 300mAg-1), with excellent reversible capacity retention of ≈79.6%. Similarly, TAPB-NDA@CNT50, when employed in sodium-ion battery (SIB), exhibited 136.7mAhg-1 specific capacity at 25mAg-1, retained ≈80% of the reversible capacity after 1000 cycles at 300mAg-1 and showing excellent rate performance. The structural advantage of TAPB-NDA@CNT will encourage researchers to design COF-based cathodes for the alkali ion batteries.

Bi-Doped P2 layered Sodium-Ion Battery Cathode with Improved Cycling Stability

P2-phased layered oxide materials have been extensively studied as cathode material for sodium-ion batteries due to their high capacities and ionic conductivities, making them promising for large-scale applications. Additionally, manganese-based compounds, with their low cost and high capacity, have attracted significant attention in recent years. However, challenges remain regarding durability issues and related structural instability caused by the Jahn-Teller effect induced by Mn3+ ions formed during the cycling process in these materials, which causes manganese dissolution during use. In this study, we introduce a cathode composition of Na0.8Mn0.75Fe0.2Al0.05O2 and show that bismuth doping enhances the structural stability of the cathode material during electrochemical cycling. Electrodes with varying levels of bismuth doping were compared in half-cell configurations; material with 1% bismuth doping demonstrated outstanding stability, retaining 95.8% capacity after 200 cycles at a 0.2 C rate through the full potential range. dQ/dV analysis shows that bismuth doping effectively suppresses the excess Mn redox, which could otherwise deteriorate the cathode structure. As a proof of concept, Bi-doped materials were implemented in full cells paired with hard carbon that exhibited much better stability than those without bismuth doping. Lastly, the moisture and air stability of the bismuth-doped electrode were tested, demonstrating good stability.

Fe-Doped NaVPO4F/C Compounds for Sodium-Ion Battery Cathodes: Electrochemical Performance and Analysis of Kinetic Properties

Fe-Doped NaVPO₄F/C Compounds for Sodium-Ion Battery Cathodes: Electrochemical Performance and Analysis of Kinetic Properties

The Progress of Cathode and Electrolyte for Low Temperature Sodium-Ion Battery

The Progress of Cathode and Electrolyte for Low Temperature Sodium-Ion Battery

Demystifying In Situ Pyrolysis Chemistry for High-Performance Polyanionic Cathodes in Sodium-Ion Batteries.

The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na3V2(PO4)3 (NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na+ migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.

Prilling and Coating Strategy to Synthesize High-Performance Spherical NaNi0.4Fe0.2Mn0.4O2 Cathode Materials for Sodium Ion Batteries.

Low-cost sodium ion batteries are of great significance in large-scale energy storage applications. With its high energy density and simple synthesis process, layered transition-metal oxides have become one of the most likely sodium ion battery cathode materials to replace lithium ion batteries in the energy storage market. Here, we report a prilling and MoS2 coating strategy to prepare the spherical cathode material. The spherical micronano particles shorten the diffusion path of Na+, restrain the complexity phase transitions, and enhance the tap density of the materials. In addition, the MoS2 coating improves the electrical conductivity of the material and the structural stability of the cathode material in air. The initial specific discharge capacity is 148.4 mA h g-1 at 0.1 C, which can be maintained at 128.9 mA h g-1 after exposure to air for 10 days. This method dramatically improves the energy density and structural stability of the cathode material, which provides a new scheme for preparing high-performance sodium ion batteries.

Pore-Free Single-Crystalline Particles for Durable Na-Ion Battery Cathodes.

The O3-type Na[Ni1-x-yCoxMny]O2 cathodes have received significant attention in sodium-ion batteries (SIBs) due to their high energy density. However, challenges such as structural instability and interfacial instability against an electrolyte solution limit their practical use in SIBs. In this study, the single-crystalline O3-type Na[Ni0.6Co0.2Mn0.2]O2 (SC-NCM) cathode has been designed and synthesized to effectively relieve the degradation pathways of the polycrystalline O3-type Na[Ni0.6Co0.2Mn0.2]O2 (PC-NCM) cathode for SIBs. The mechanically robust SC-NCM due to the absence of pores in the particles enhances tolerance to particle cracking, resulting in stable cycling performance with a cycle retention of 73% over 350 cycles. Moreover, the proposed SC-NCM is synthesized using a simple and cost-effective molten-salt synthetic route without the complex quenching process typically associated with PC-NCM synthesis methods, showing good practical applicability. This study will provide an innovative direction for the development of advanced cathode materials for practical SIBs.

Entropy Strategy for Stabilizing O′3-NaMnO2-Layered Cathodes for Sodium-Ion Batteries

Entropy Strategy for Stabilizing O′3-NaMnO₂-Layered Cathodes for Sodium-Ion Batteries

Understanding the Role of Mn Substitution for Boosting High-Voltage Na4Fe3-xMnx(PO4)2P2O7 Cathode in Sodium-Ion Batteries.

Na4Fe3(PO4)2P2O7 is regarded as the most promising polyanionic cathode for sodium-ion batteries (SIBs) due to its superior structural stability, cost-effectiveness, and environmental benignity. However, the low operating voltage inevitably weakens its competitiveness in energy density. Previous works have tried to enhance its operating voltage by Mn doping, which draws on the design idea of LiFexMn1-xPO4 cathode for lithium-ion batteries, but with little success. In this context, uncovering the role of Mn substitution in Na4Fe3-xMnx(PO4)2P2O7 (NFMxPP) cathode is urgently needed. This work discloses the effect of Mn contents on the structure, sodium storage property, and reaction mechanism of NFMxPP cathode for the first time. Introducing a moderate amount of Mn (0.6 ≤ x ≤ 1.2) into NFMxPP can weaken the Fe-O bonding interaction, thus leading to the full utilization of Mn3+/Mn2+ redox couple. As the representative, NFM1.2PP cathode exhibited a high operating voltage of ≈3.3V with a reversible capacity of 109.2 mAh g-1. Note that a Hard carbon||NFM1.2PP full battery manifests considerably high-capacity retention of 92.3% over 1600 cycles. It is believed that an understanding of the role of Mn substitution in this work will promote the practical application of high voltage NFMxPP cathodes for SIBs.

Preparation and application of high-performance sodium-ion batteries cathode material Na3.6Fe2.6(PO4)1.6P2O7 with optimized sodium-iron ratio

Na4Fe3(PO4)2P2O7 (NFPP) has been developed as the most promising polyanion cathode for sodium-ion batteries due to its excellent electrochemical performance, high safety properties, and environmental friendliness. However, the electrochemically inactive impurity (m-NaFePO4) will inevitably generate during synthesis process, which decreases the practical capacity of NFPP significantly. In this paper, a novel Na3.6Fe2.6(PO4)1.6P2O7 cathode material with excellent performance is successfully exploited by optimizing sodium-iron ratio to reduce the formation of impurity phases. In a series of as-prepared materials with sodium-iron ratio between 1.33–1.50, Na3.6Fe2.6(PO4)1.6P2O7 exhibits the highest discharge specific capacity (110.3 mAh g−1 at 0.1C), best rate capability (84.4 mAh g−1 at 30 C) and cycle performance (78.2 % capacity retention after 3000 cycles at 20 C). Furthermore, 20 Kg of the Na3.6Fe2.6(PO4)1.6P2O7 cathode material is prepared by spray drying method, which has been successfully applied in sodium-ion pouch cells (12 Ah) with a commercial hard carbon as the anode materials. The assembled pouch cells display excellent cycle performance (82.4 % capacity retention after 2000 cycles at 1 C), rate capability (88 % capacity retention at 30 C) and low-temperature performance (74 % capacity retention at −40 °C).